1. Field of the Invention
The present invention relates to an alarm device, and more specifically to an alarm device, which is designed so as to provide sufficiently high detection sensitivity for a sensor mounted therein.
2. Description of the Related Art
In recent years, the use of antitheft device for vehicles is now widespread to prevent the theft of a vehicle. In such an antitheft device for vehicle, an ultrasonic sensor, infrared sensor or the like is used to detect the crack of a glass, the opening/closing of a door and others, thereby enabling a warning signal to be sounded for an abnormality.
As an antitheft device, there is a simple antitheft device for vehicle, whose main body can be mounted either onto the dashboard in the vehicle or onto a sun visor, wherein an exclusive plug for power supply is used to insert into a socket for cigarette lighter.
FIG. 1 shows an exemplified structure of a conventional antitheft device for vehicle (disclosed in “New Product Information”, on-line searched on Nov. 27, 2002 by the Internet, http ://www52.tok2.com/home/cellstar/pdf/RP-210S_P56xJd4jVhWhQ.pdf). The antitheft device for vehicle in FIG. 1 comprises a main body 1 having a microcomputer for controlling various components constituting the antitheft device for vehicle; a sensor section 2 disposed inside the vehicle for monitoring the inside thereof, using an infrared sensor; and a hinge 3 for pivotally connecting the main body 1 to the sensor section 2.
The main body 1 is equipped with a fitting 4 having an approximately U-shaped section for inserting a sun visor 6 thereinto. A user can mount the antitheft device for vehicle in the inside of the vehicle by inserting the fitting 4 into the sun visor 6 in the direction of arrow shown in FIG. 1.
The hinge 3 includes a screw for adjusting the angle between the sensor section 2 and the main body 1. The screw serves to pivotally support the sensor section 2 within a angular range of inclination, where the sensor section 2 comes in contact with the main body 1, and therefore is held there at the maximum tilting angle. Accordingly, the user is able to adjust the angle between the sensor section 2 and the main body 1 by rotating the sensor section 2 around the screw axis.
FIG. 2 shows an exemplified structure of another conventional antitheft device for vehicle (disclosed in “The Alarm Device for Theft inside Vehicle”, on-line searched on Nov. 27, 2002 by the Internet, http://dmedia.new.co.jp/nais-automotive/autopolice/index.htm). The antitheft device for vehicle shown in FIG. 2 comprises a main body 11 having a microcomputer for controlling various components constituting the antitheft device for vehicle and the sensor member 12 constituted by an infrared sensor for monitoring the inside of the vehicle.
The sensor member 12 is disposed in front of the main body 11 (on the left hand side in FIG. 2) such that it projects from the main body 11. Moreover, the main body 11 includes a microphone (not shown) for detecting a sound in the inside of the vehicle.
The antitheft device for vehicle can also be easily mounted onto a sun visor 13 with the aid of a fitting (not shown) mounted to the main body 11, as shown in FIG. 2.
As described above, since the antitheft device for vehicle can easily be mounted into the vehicle, any general user having no professional knowledge is able to mount the device with ease.
However, the antitheft device for vehicle in FIG. 1 requires adjusting the angle of the sensor section 2 relative to the main body 1 after the main body is mounted onto the sun visor 6, and the angle adjustment takes a lot of time and effort for a user. Moreover, there is a possibility that the sensor section 2 cannot be set at a proper angle if the general user having no professional knowledge tries to adjust the angle of the sensor section 2. In such a case, the sensor section 2 cannot provide sufficiently high detection sensitivity.
Moreover, there is a possibility that the user inserts a receipt of the admission fee to a high way or a parking coupon into the sun visor of the vehicle. As a result, when such a user inserts, for example, a receipt 14 of the admission fee to high way between the sun visor 13 and the main body 11 in the antitheft device for vehicle shown in FIG. 2, since the sensor member 12 projects from the main body 11, the receipt 14 thus inserted is in contact with the sensor member 12, as shown by the broken line in FIG. 2, or it covers the sensor member 12. In such a case, there is a problem for the sensor member 12 that the sensor member 12 cannot provide sufficiently high detection sensitivity.
Moreover, the microphone installed in the antitheft device for vehicle shown in FIG. 2 is aligned, for example, in the direction toward just below the antitheft device for vehicle mounted into the sun visor 13. Accordingly, the sound emitted just below the antitheft device for vehicle (toward the front of the vehicle) can be effectively detected. However, it is difficult to detect the sound emitted backward in the inside of the vehicle.